Liquid-crystal (L-C) polymers are known to form mesophases having one- and two-dimensional order as disclosed by Flory, P. J., Advances in Polymer Science, Liquid Crystal Polymers I; Springer-Verlag: New York (1984) Volume 59; Schwarz, J. Mackromol, Chem. Rapid Commun. (1986) 7, 21. Further, mesophases are well known to impart strength, toughness and thermal stability to plastics and fibers as described by Kwolek et al in Macromolecules (1977) 10, 1390; and by Dobb et al, Advances in Polymer Science, Liquid Crystal Polymers II/III (1986) 255(4), 179.
While L-C polymers have been widely studied, their potential utility as coatings binders seems to have been overlooked. Japanese patents claiming that p-hydroxybenzoic acid (PHBA), a monomer commonly used in L-C polymers, enhances the properties of polyester powder coatings are among the very few reports that may describe L-C polymers in coatings; Japanese Kokai 75/40,629 (1975) to Maruyama et al; Japanese Kokai 76/56,839 (1976) to Nakamura et al; Japanese Kokai 76/44,130 (1976) to Nogami et al; and Japanese Kokai 77/73,929 (1977) to Nagami et al.
Hardness and impact resistance are two desirable characteristics of coatings. However, because hardness is associated with higher T.sub.g s (glass transition temperatures), and good impact resistance with lower T.sub.g s, there is usually a trade-off between hardness and impact resistance. Further, non-baked polymeric vehicles with low viscosities which provide binder coating films with improved hardness and shorter drying times through combinations of polymers with mesogenic groups are not disclosed in the prior art and are to be desired.
An object of this invention is the provision of modified polymers comprising low Tg polymers covalently bonded with mesogenic groups for use in formulated coatings to provide improved films.
A more particular object of this invention is to provide enamels of improved hardness and impact resistance.
Other important objects are to provide high solids/low viscosity, non-baking formulated coatings comprising polymeric vehicles for providing films wherein the coating formulation is fast drying and provides hard and impact resistant films.
Still further objects and advantages of the invention will be found by reference to the following description.